html, body {
    margin: 0 0 0 0;
}
#wrapper {
    padding-top: 80px;
    margin-bottom: 20px;
}
#pre {
    background-color: black;
    color: white;
    padding: 10px 10px 10px 10px;
}
#qrcode-container {
    display: flex;
    justify-content: center;
    align-items: center;
}

div {
    margin-top: 5px
}
nav {
    padding: 20px 20px 20px 20px;
    background-color: rgba(0,0,0,0.1);
    width: 100%;
    position: fixed;
    top: 0;
}
nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
}
nav ul li {
    display: inline;
    padding: 0px 10px 0px 10px;
}
nav ul li.active {
    background-color: black !important;
    padding: 10px 10px 10px 10px;
}
nav ul li a {
    text-decoration: none;
    font-weight: bold;
}
nav ul li a.active {
    color: white;
}